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Th 
to 


Th 
po 
of 
fill 


Or 

be 
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sic 

oti 
fir 
sic 
or 


Th 
sh 
Til 
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Mi 
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be 
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0 


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10X 

14X 

18X 

22X 

26X 

30X 

J 

12X 


16X 


20X 


24X 


28X 


32X 


trails 
I  du 
odifier 
-  une 
mage 


The  copy  filmed  hare  has  baan  raproducad  thanks 
to  tha  ganarosity  of: 

Library, 

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plus  grand  soin,  compte  tsnu  de  la  condition  at 
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conformity  avec  lea  conditions  du  contrat  de 
f<lmage. 


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Lea  exemplaires  origir.aux  dont  la  couverture  an 
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par  le  premier  plat  at  an  tarminant  soit  par  la 
darniire  page  qui  comporte  une  ampreinte 
d'impreaaion  ou  d'illuatration,  soit  par  la  second 
plat,  seion  le  caa.  Toua  lea  autraa  sxempiairas 
origtnaux  sont  filmte  an  commandant  par  la 
premiere  page  qui  comporte  une  ampreinte 
d'impreaaion  ou  d'illuatration  at  an  tarminant  par 
la  derniire  page  qui  comporte  une  telle 
empreinte. 


The  laat  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  —^(meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 


Un  d^  symboles  suivants  apparaitra  sur  la 
damiire  image  de  cheque  microfiche,  seion  le 
caa:  le  symboie  ~»  signifie  "A  SUIVRE ',  le 
symboie  V  signifie  "FIN". 


Mapa.  plfitaa.  charts,  etc.,  may  be  filmed  at 
different  reduction  ratioa.  Thoae  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hand  comer,  left  to 
right  and  top  to  bottom,  aa  many  framea  aa 
required.  The  following  diagrama  illustrate  the 
method: 


Laa  cartea.  planches,  tableaux,  ate,  pauvent  atre 
fiimte  it  dea  taux  de  rMuction  diff  Arents- 
Lorsque  le  document  est  trop  grand  pour  dtre 
reprnduit  en  un  seul  cliche,  ii  est  filmd  <i  partir 
d«  I'angia  sup^rieur  gauche,  de  gauche  ^  droite, 
et  da  haut  en  baa,  an  prenant  le  nombre 
d'images  nteeasaira.  Lea  diagrammes  suivants 
iilustrant  la  m^thode. 


irrata 

to 


pelure. 
n  a 


1  2  3 


32X 


12  3 

4  5  6 


m  24 


[Extracted  Jrom  the  Proceedings  of  the  Rochester  Academy  of  Science,  Volume  9i\ 


ESKERS  NEAR  ROCHESTER,  "N.  Y. 


By  Warren  Upham. 


Rochester,  N.  Y. 

Published  by  the  Society, 

February,  1893. 


1 


\F.xtractt(i  from  f/ir  Procia/iin's  of  t/tr  Roclic^tcr  Academy  of  Siintir,  Volunw  :.| 


ESKKRS  NKAR    K()CIIi:si  1:R,   N.   V 


A     l)I?CU>>Ili\    Ol'     THi: 


-TRL'ClfKK    AND    ORK.IN    or     rui:    IMNXACI.E 
Uv    WaKKI.N    Ul'HA.M. 


CONTENTS. 


Pa, 


Tlic  Area  specially  studied 

Description  of  the  I'innacle  Hills 

Relationship  to  tlie  surroiindiny  Country 

Altitudes  in  Rocliester  and  its  Vicinity 

Eskers  in  I'ittsfcjrd 

Relationship  to  Druinlins  and  Terminal  Moraines  on  the 

Relationship  to  (Hacial  Movements 

Probable  Orijjin  of  these  Eskers 

Application  of  this  Explanation  to  Eskers  elsewhere , 


H. 

iSi 
182 
I  {7 
1S8 


)Uth. 


'I"HE  Area  specially  studied. 

On  the  southeastern  border  of  Rochester,  X.  Y.,  a  remarkable 
esker  series,  named  the  I'innacle  hills,  extends  nearly  four  miles 
from  east-northeast  to  west-southwest,  rising  from  an  approximately 
level  country  and  forming  the  only  conspicuous  elevations  of  land 
close  to  that  city.  Under  the  guidance  of  Mr.  (r.  K.  Gilbert,  this 
esker  was  examined  by  most  of  the  geologists  who  attended  the 
meetings  of  the  Geological  Society  of  America  and  of  Section  E  of 
the  American  Association  for  the  Advancement  of  Science  in  Roch- 
ester last   August,  and  on  the  following  morning  about  an  hour  was 


•This  paper  was  ori^'inally  prepared  lor  and  read  at  the  (ittawa  meeting  of  the  Cieolugiiai 
Society  of  America,  December  ., ,  li.j 


I82 


!<()(   HKSTKR    .\(  AI>I.MV    OC    SCIF.NCE. 


[Jan.  9, 


given  to  discussion  of  the  manner  of  its  formation  through  the  agency 
of  the  ice-sheet  and  the  streams  produced  l)y  its  melting.  liefore 
stating  some  of  the  opinions  brought  out  in  that  discussion,  and 
attempting  a  full  incpiiry  concerning  the  processes  of  accumulation  of 
this  and  other  eskers  and  kames,  we  will  first  go  again,  as  I  did  on 
following  days,  over  the  Pinnacle  hills  and  describe  their  contour  and 
numerous  sections  exposed  by  excavations  for  road  material  and 
for  the  passage  of  streets.  The  other  drift  deposits  and  contour  of 
their  vicinity  will  be  noted,  and  a  second  series  of  eskers  Iving  .several 
miles  farther  southeast  in  Pittsford,  which  I  also  examined,  will  be 
described,  with  their  relationship  to  prominent  drumlins  near,  and  to 
terminal  moraines  more  remote,  on  the  south. 

Descrii'iion  (II    niK  Pinx.xci.k  Hills. 

From  lirighton  village  and  station  on  the  New  ^'ork  Central  rail- 
road, thrc.    miles  southeast  from  the  .station  in  Rochester,  this  promi- 
nent range  of  hills  extends  in  an  almost  straight  course  about  four 
and   a  half  miles  west-southwesterly  to  the  (lenesee  river  close  south 
of  the  State  dam.     In   passing  the  east  end  of  this  e^ker,  the   Erie 
canal  turns   from  a  due  east  to  a  due  south  course.       Along  its   first 
mile  from  lirighton  the  esker  rises  75  to  150  feet  above  the  country 
on    each  side,  and  declines  in  height  from   125  to  75  feet  near  the 
western  end  of  this  portion,  where  it  is  known  as  Cobb's  hill.    Imme- 
diately to  the  west,  near  the   residence  of  Mrs.  \V.  H.  Cobb,  a  sag  in 
the  esker,  as  it  was  originally,  before  being  cut  down  for  the  extension 
of  Monroe  avenue,  had  a  heigiit  of  only  about  50  feet.      Next  west- 
ward the  esker  rises  in  the  distance  of  a  hall  mile  to  its  highest  point, 
called    the    Pinnacle,    200  feet   above   the   nearly  plain  region  on  the 
north  and  sjuth.     Thence  the  continuation  of  the  esker  along  its  next 
two  miles,  varying  in  altitude  mainly  from   150  to  100  feet  above  the 
general    level,    is   occupied,    in   order  from  ea^t   to  west,    by  the  St. 
Patrick  Cemetery,  the  Highland  Park,  which  includes  the  Mt.  Hoi)e 
reservoir  in  its  western   part,  and  the  extensive  Mt.  Hope  Cemetery 
In  its  next  mile  west  to  the  river,  the  ridge  is  lower,  having  a  height 
uf  only  80  to  50  feet  above  the  State  dam.      The  northeastern  end  of 
this  hill  range  at  Prighton  is  very  definite,  overlooking  a  wide  expanse 
of  the  low  land  ;  but  its  western  end  is  indefinite,  for  in   the  line  of 
its  continuation  west  of  the  (Jenesee  it  is  represented  along  a  distance 
of  at  least  two  miles  (which  is  as  far  as  my  examination  extended)  by 
a  low  ridge,  mostly  30  to  40  feet  ab(;ve  the  general  level.       Petween 


•    •••>•«*      •» 


♦  •        •  .  ••  •     /•  ••  •       •  •       •        • 


•#'•         ••#••,••••, 


««93-] 


UHHAM — ESKERS    NEAR    ROCHESTER,    N.  Y. 


183 


the  Mount  Hope  Cemetery  and  the  (lenesee  river  and  farther  to  the 
west,  the  material  of  the  ridge  is  'argely  till,  which  shows  that  low 
portion  to  be  a  marginal  or  interlobate  moraine  ;  but  the  high  range 
of  the  Pmnacle  hills  from  Brighton  to  the  Mt.  Hope  Cemetery  i.s 
clearly  an  esker,  3/,  miles  long,  consisting  of  interbedded  gravel  and 
sand,  here  and  there  enclosing  boulders,  sometimes  in  surprisintr 
abundance,  but  containing  no  till  in  the  extensive  sections  nor  on  its 
surface. 

The  width  of  this  hill   range  is  mostly  about  a  sixth  of  a  mile 
but  vanes  from  a  tenth  to  a  half  of  a  mile.      Along  its  whole  extend 
It  IS  a  smgle  range,  nowhere  presenting  a  combination  of  parallel 
series  of  hdls  ;  but,  in  some  parts,  especially  in   the  Highland  Park 
and  near  the  reservoir,  it  is  incised  on  each  side  by  ravines  between 
spurs  and  outlying  hillocks  of  the  main  belt,  and  its  top  is  occasion^ 
ally  very  uneven  in  contour,  with  infrequent  bowl-shaped  hollows  lo- 
to  50  feet  below  the  surrounding  surface.     The  profile  of  its  crest  line 
undulates    in    an   irregular  way,  generally  varying  50  to  100  feet  in 
height  upon  each  mile  or  half  mile  ;  and  it  nowhere  maintains  a  level 
course  for  any  considerable  distance.     In  the  vicinity  of  the  Pinnacle 
and    :n  many  other  places,  the  slopes  on  each  side  are  very  steep 
ranging  to  a  maximum  of  about  30  degrees  ;  and  the  crest  line  has 
occasional  slopes  of  half  this  steepness.      More  commonly,  however 
the  slopes  vary  from  6  to  15  degrees,  having  from  10  to  2s   feet    of 
ascent  in  a  distance  of  100  feet. 

When   my  first  contribution   to  geology  was  published,  sixteen 
years  ago,  "  On   the   origin  of    Kames   or   Eskers   in    New   Hamp- 
shire, •  (■)  these  classes  of  the  modified  drift,  produced  jointly  by  the 
ice-sheet  and  the  water  of  its  melting,  had   not   been    discriminated 
from  each  other.     Every  knoll,  hillock  or  hill,  short  or  long  ridge  or 
series  or  network  of  ridges  composed  of  irregularly  and  often  aiui- 
clmally  bedded  gravel  and  sand,  retaining  nearly  the  original  form  in 
which  It  was  accumulated,  was  then  called  interchangeably  a  kame 
esker,  or  as,  or  a  series  of  /cames,  eskers,  or  asar.     The  first  of  these 
terms  is  of  Scottish,  the  second  of  Irish,  and  the  third  of  Scandina- 
vian origin,  the  last  being  Anglicized  to  ^.ar,  with  .w.  as  its  pluril 
form.      It  is  found  very  desirable,  however,  to  subdivide  these  gravel 
and  sand  accumulations  into  two  classes,  as  proposed  by  McGee  n 
and  Chamberlin,  (')  giving  to  the  hillocks  and  short  ridges  the  name 

{.  )     Proc.  A.  A    AS.,  Vol.  .XXV,  for  ,87^  pp.  =,fi-.2, 


I.S4 


KOt  IIKSI  KU    A(  ADIMV    OK    SCIKNl.K. 


[Jan.  9, 


/ciiiiia,  while  the  prolonged  ridges  are  termed  /'.vXr/.v  or  osars,  exceiiting 
tlicir  neciiliar  development  in  northeastern  Iowa,  where  they  are  com- 
posed chietly  of  loess  or  fine  silt  and  have  received  the  name  /(///r/, 
alike  whether  singular  or  jjliiral.  (')  Kanu-s,  as  thus  detined,  usually 
or  often  constitute  an  imi)ortafl  part  of  the  terminal  moraines,  and  they 
are  also  frecpient  on  many  other  jjortions  of  our  drift  sheet.  Kskers 
are  found  likewise  both  in  the  vicinity  of  terminal  moraines,  some- 
times being  evidently  of  closely  contemporaneous  origin,  and  also 
remote  from  moraine  belts.  In  length  the  eskers  or  osars  vary  from 
a  mile  or  less  to  several  miles,  and  in  Maine  and  Sweden  they  extend 
in  many  continuous  series,  20,  50,  and  even  100  miles  or  more.  Their 
courses  are  commonly  somewhat  crcjoked,  like  those  of  rivers,  but  in 
general  they  run  in  parallelism  with  the  glacial  stria;  and  directions 
in  which  the  ice-sheet  moved  ami  carried  its  boulders  and  other  drift. 

The  structure  of  the  Tinnacle  hills  esker  is  well  exhibited  near 
its  northeast  end,  near  Monroe  avenue,  and  at  various  places  separa- 
ted only  by  short  intervals,  thence  westward  to  Mt.  Hope  avenue  and 
cemetery,  by  excavations  for  the  use  of  its  gravel  and  sand  in  road- 
making  and  masonry.  Less  than  a  quarter  of  a  mile  south  of 
iirighton,  a  cut  on  the  northern  slope  of  the  east  end  of  the  esker,  just 
east  of  the  north  to  south  road  (.\rbutus  avenue),  has  a  depth  of 
about  30  feet  and  length  of  some  12  rods.  The  upper  10  feet  are 
fine  gravel  and  sand,  almost  levelly  bedded,  beneath  which  the  remain- 
der of  the  section  consists  of  very  coarse  but  distinctly  stratified 
gravel,  with  a  nearly  uniform  dip  of  15"  W.  S.  \V.  'i'liis  coarse  gravel 
contains  cobbles  and  rock  fragments  of  all  sizes,  up  to  ij^  feet  in 
length,  packed  closely  together,  their  interstices  bei  ig  fdled  with  liner 
gravel,  sand,  and  very  line  silt.  About  two  thirds  of  all  the  stones 
art'  much  water-worn,  so  as  to  have  rounded  forms  ;  nearly  all  of  the 
remaining  third  are  somewhat  worn,  being  subangular  ;  and  only 
about  a  twentieth  part  are  rather  sharply  angular,  with  little  or  no 
evidence  of  attrition  in  their  transportation  by  the  glacial  river.  ]''ully 
half  of  the  small  gravel,  up  to  six  inches  in  diameter,  are  Medina 
sandstone  ;  and  about  a  third  of  the  cobbles  and  masses  from  6  to 
18  inches  in  diameter  are  Archivan  gneissoid  rocks.  Only  four  bould- 
ers of  larger  size,  none  of  these  exceeding  four  feet  in  diameter,  were 
seen  in  this  section. 

Close  west  of  this  road,  nearly  opposite  to  the  foregoing  and  at 
a  distance  of   10  to   30  rods   southwest   from  it,  a  larger  excavatit)n. 


*'•'.  ^y  -' .^'K^'S*-'-  ','  ''"^  I'lL'istcKcne  Historvof  in.rthciistcrn  Inwa,"  in  llic  Kltven'.li  .Amuia 
Kcport  (il  tlic  L  .  S.  (itcil.  Survey,  fur  iSSy->ji.). 


'«93.] 


iri'HAM— KSKF.RS    NKAR    KOCHKSTKK,    N.   V. 


'85 


also  in  the  northern  side  of  the  esker.  consists  almost  wholly  of  fine 
jrravel  and  sand,  with  stratification  mostly  inclined  5"  to  20"  south- 
ward.     This  section,  30  to  40  feet  deep,  and  the  surface  of  the  esker 
immediately  adjoining  it,  have  only  very  rare  boulders  ;  but  within  a 
short  distance  the  southern  slope  of  the  ridge,  where  it  is  cut  for  the 
road,  has  many  boulders  on  the  surface  and  in  the  uuper  10  feet  of  the 
k'ravel   and  sand.      The  rather  broadly  rounded  toj)  of  th^    ^sker  is 
here  about  So  feet  above  the  general  level  on  the  north,  east  and  south. 
In  its  central  part,  .-5  feet  below  the  top  and  some  20  rods  from  its 
northern  ba.se,  a  small  space  of  this  section,  10  feet  long  and  6  feet  in 
height,  shows  three  sharp  faults,  each  having  2  to  3  feet  of  displacement, 
with  overthrust  from  south  to  north.      The  beds  overlying  the  faulted 
portion,  which  was   near  the  bottom  of  the  e.vcavation,  and  the  con- 
tinuations of  the  faulted  layers  away  from  this  place  on  each    side, 
were  undisturbed,  dipping  10"  to  15"  S.  or  S.  S.  W.       Fifteen    to   40 
teet  east  from  these  faults,  slightly  higher  beds  show  eight  repetitions, 
within  a  thickness  of  8  feet,  of  layers  of  gray  gravel,  3  to  12  inches 
thick,   separated    by  layers  of  fine   yellow  sand   .   to  3  inches    thick, 
'I'hese  alternations  probably  represent  the  rapid  and  strong  currents  of 
a  glacial   river  during  the  fast  melting  of  the  ice  surface  by  day  and 
the  slow  currents  at  night,  when  ablation  was  at  its   minimum  or 
ceased. 

Another  large  excavation  300  to  500  feet  we.st  of  the  last,  like- 
wise in  the  northern  side  of  the  esker,  has  a  vertical  face  of  40  to  50 
feet,  consisting  of  intcrbedded  gravel  and  sand  in  its  upper  half,  while 
its  lower  half  is  mostly  sand.  'I'he  largest  cobbles  in  the  gravel  are 
about  one  foot  in  diameter,  and  no  boulders  were  observed.  Mainly 
the  dip  is  10"  to  20"  southward,  but  at  the  east  end  of  this  section  it's 
upper  10  to  15  feet  are  much  contorted,  with  a  prevailing  northerly 
dip  of   10"  to  15". 

Jn  the  southeastern  side  of  the  esker,  opposite  to  Mr.s.  \V.  H. 
Cobb's  house,  an  excavation  about  25  rods  long  and  50  to  60  feet 
high  consists  in  its  upper  part,  to  a  depth  of  6^0  20  feet  from  the 
surface  along  its  whole  extent,  of  sand  and  very  coarse  gravel  enclos- 
mg  exceedingly  abundant  boulders  of  all  sizes  up  to  6  or  S  feet  in 
diameter,  far  more  plentiful  than  in  the  ordinarv  till  of  this  region. 
15elow  this  portion,  the  remainder  of  the  section,  extending  downward 
30  to  40  feet,  is  irregularly  interstratified  gravel  and  sand,  with  only 
infiajuent  boulders.  The  whole  section  shows  stratification  by  cur- 
reiiLs  of  water,  and  according  to  my  estimate  nineteen  twentieths  of 


i86 


KoiUKSIKK    ACADK.MV    OP    SCIKN(  K. 


I  Jail.  9. 


the   gravel  and  small  rock  fragments  are  rouiuled  or  at  least  mucii 
worn  on  their  edges  and  corners. 

Other  sections  which  were  examined  in  our  excursion  on  the 
northern  slope  of  the  esker  near  this  place  and  about  a  quarter  of  a 
mile  to  the  northeast,  show  the  same  astonishing  profusion  of  boul- 
ders with  the  upjier  coarse  gravel,  underlain  by  beds  having  fewer 
boulders.  The  gravel  and  sand  are  characterized  by  irregular  and 
often  oblicpie  bedding,  variable  thickness  of  individual  layers,  and 
occasional  oblique  or  nearly  vertical  faults  with  small  amount  of  dis- 
placement (').  Boulders  are  also  strown  in  considerable  numbers  on 
the  surface  of  this  part  of  the  esker,  but  elsewhere  along  most  of  its 
extent  they  are  usually  rare  both  on  the  surface  and  in  excavations. 
Mr.  (lilbert  called  attention  to  the  origin  of  the  boulders,  and  pointed 
out  the  very  significant  fact  that  many  of  them  are  of  the  Niagara 
limestone,  which  can  have  been  transported  no  moie  than  three  or 
four  miles  from  its  parent  ledges,  since  the  northern  limit  of  this 
formation  lies  within  that  distance.  Some  of  these  boulders  were 
seen  on  or  near  the  Pinnacle,  at  least  ^oo  feet  above  the  outcrops  on 
the  plain  country  northeastward  from  which  they  must  have  been 
derived. 

Continuing  over  the  Pinnacle  and  through  the  Highland  Park,  I 
examined  numerous  sections,  all  of  which  were  interbedded  gravel 
and  sand  vyith  only  very  rare  boulders  or  more  commonly  none.  Occa- 
sionally, however,  a  boulder  5  or  even  10  feet  in  diameter  is  found  on 
the  surface,  or  in  a  section,  remarkably  in  contrast  with  the  water- 
deposited  sand  and  gravel,  in  which  the  largest  pebbles  and  cobbles 
range  from  a  few  inches  to  a  foot,  or  seldom  one  and  a  half  feet  in 
diameter.  l-'rom  the  Pinnacle  to  the  Mount  Hope  cemetery,  most  of 
the  excavations  are  chiefly  sand. 

The  cut  made  west  of  this  cemetery  by  a  branch  of  the  New 
York,  Lake  Erie  &  Western  railroad  has  a  length  of  nearly  a  quarter 
of  a  mile  from  north  to  south  and  is  from  15  to  25  feet  deep.  Large 
portions  of  this  section  are  true  till,  or  clay,  sand,  and  small  and  large 
rock  fragments,  mingled  in  an  unstratified  deposit ;  but,  like  the  till 
of  the  surrounding  country,  it  contains  only  few  large  boulders. 
Among  the  half  dozen  boulders  of  greater  size  than  two  feet  in 
length  seen  in  the  eastern  face  of  this  excavation,  oae  of  the  largest, 
about  five  feet  in  diameter,  was  Niagara  limestone.    With  the  depos- 


(i.)  Numbers  323,  324  and  325  of  the  list  of  photographs  of  the  Geological  Society  of 
America  (Bulletin,  G.  S.  A.,  Voi.  Ill,  p.  472*  are  views  of  sections  of  the  Pinnacle  hills  esker  at 
this  locality,  photographed  and  piescnled  by  Professor  H.  L.  Fairchild. 


»893.I 


UI'HA.M — KSKEkS   NEAR    RUCUESTER,    N.  V. 


187 


its  of  till  are  many  intercalated  layers  of  stratified  sand,  from  i  to  5 
feet  in  thickness,  often  continuous  along  a  distance  of  100  feet  or 
more.  These  lay  ;s  are  mostly  horizontal  or  only  slightly  inclined, 
and  no  contortion  nor  evidence  of  erosion  or  tumultuous  pushing  for- 
ward was  observed. 

Beyond  its  intersection  by  the  Genesee  river,  this  ridge  is  the  rite 
of  the  Rapids  Cemetery,  and  thence  it  extends  nearly  due  west  two 
miles  along  or  close  to  Hrooks  avenue.  It  rises  by  usually  gentle 
slopes  ,?o  to  40  feet  above  the  land  on  its  south  and  north  sides,  and 
has  a  width  of  25  to  50  rods,  being  often  quite  irregular  in  contour, 
whirh  with  its  clayey  soil  and  occasional  boulders,  gives  it  a  morainic 
aspect.  Where  it  is  cut  by  the  Hulfalo,  Rochester  ^:  I'ittsburgh  lail- 
road,  nearly  two  miles  west  of  the  river  and  between  an  eighth  and  a 
third  of  a  mile  north  of  Hrooks  avenue,  several  recent  excavations 
si  Nved  about  half  of  its  material  to  be  till,  and  the  remainder  very 
compact  stratified  sand.  These  unlike  deposits  are  irregularly  accu- 
mulated together,  but  no  interblending  was  seen.  The  till  has  no 
marks  of  water  action,  and  the  sand  is  free  from  boulders  or  gravel, 
and  is  horizontally  bedded  or  nearly  so,  being  sometimes  5  to  15  feet 
thick  with  an  exposed  extent  of  fully  100  feet. 

Rt'latioHship  to  the  surrouihiin;^  6^tf//«/;j'.— Throughout  the  city  of 
Rochester,  excepting  the  Pinnacle  hills  and  the  gorge  of  the  Genesee 
below  its  falls,  the  surface  is  nearly  a  plain,  with  slight  descent  toward 
I-ake  Ontario.  The  underlying  Niagara  and  Clinton  formations  are 
covered  generally  with  only  10  to  20  feet  of  drift,  which  is  mainly  Lill 
and  in  small  tracts  stratified  clay  or  sand  and  fine  gravel.  North- 
ward from  Rochester,  the  surface  in  Irondequoit  and  Greece  town- 
hips  declines  with  a  gradual  slope  200  to  250  feet  in  the  distance  of 
5  to  7  miles  to  Lake  Ontario. 

The  fjord-like  Irondequoit  bay,  lying  between  Irondequoit  town- 
ship on  the  west  and  Webster  and  Penfield  on  the  east,  stretches  about 
'(w^  miles  southward  from  Lake  Ontario,  with  a  width  varying  from 
one  m.le  to  a  half  mile,  bordered  by  clil't's  100  to  200  feet  high,  which 
rise  to  the  general  plain  on  each  side.  The  maximum  depth  of  Iron- 
de(iuoit  bay  is  80  feet,  which  must  be  added  to  the  height  of  the  bluffs 
to  give  the  total  depth  of  the  eroded  valley ;  and  its  southern  end, 
where  the  Irondequoit  river  flows  into  it,  is  about  five  miles  east  from 
the  center  of  Rochester.  Before  the  Ice  age  the  Genesee  doubtless 
enteied  the  lake  through  this  valley,  probably  leaving  its  present 
course  near  the  mouth  of  the  Honeoye  creek,  flowing  eastward, 
through  Bush  township  and  the  southern  part  of  Mendon,  and  thence 
northward  along  the  Irondequoit  river  and  bay.     In  the  southeast 


I 


iSS 


ROCHESTER    ACADK.MV    OK    SCIK.NCE. 


[Jan.  9. 


edge  of  I'ittbford  tlie  Irondeiiuoit,  where  it  is  crossed  by  the  Erie 
canal  and  for  three  miles  southward,  is  about  loo  feet  lower  than  the 
Genesee  near  the  south  line  of  the  city  of  Rochester,  above  the  State 
dam.  Rspecially  thick  accumulations  of  the  glacial  drift  in  Memlon 
caused  the  (lenesce  after  the  Ice  age  to  take  its  new  course  through 
Rochester ;  and  its  rock  gorge,  extending  from  the  center  of  this  city 
to  its  mouth  at  Charlotte,  has  been  eroded  during  the  Postglacial  or 
Recent  ei)och,  of  which,  like  the  gorges  below  the  falls  of  Niagara 
and  of  St.  Anthony,  it  affords  a  means  of  measurement,  if  the  e.xtent  of 
recession  of  the  Genesee  falls  during  the  present  century  can  be 
determin  'd. 

Southward  and  eastward,  elevations  of  equal  height  with  the 
I'innacle  hills  are  first  found  at  the  distance  of  7  to  10  miles,  being 
prominent  drift  accumulations  later  to  be  described  in  this  paper, 
lying  in  the  southwest  part  of  I'ittsford  ^  id  northwestern  Mendon. 
and  between  Victor  and  Kairport. 

'l"he  1  elation  of  the  Pinnacle  i.llls  to  the  adjoining  region  will 
be  further  exhibited  by  the  following  list  of  altitudes,  which  are 
mostly  derived  from  maps  in  the  oflice  of  Mr.  J.  V.  McClintock,  city 
engineer  of  Rochester,  others  being  from  the  tJnited  States  Lake 
Survey.     They  all  are  referred  to  mean  tide  sea  level. 


Altitudes  in  Rocliestcr  and  its  I'icinity. 

1 

Lake  Ontario,  low  and  high  water,  2\^-2^,^)  ;  ordinary  stage.  . 

Irotjuois  beach,  between  Irondecjuoit  bay  and  the  Genesee 
river  (Gilbert) 

Erie  canal,  coping  and  tow-[)ath  of  viaduct  crossing  the  Cicn- 
esee  river  in   Rochester,  510;  water _. 

New  York  Central  railroad  track  at  Rochester    station 

Wide  Waters  of  the  Erie  canal  on  southeastern  line  of  Roch- 
ester  

Railroad  at  Brighton  station .  _ 

Can  J ,  at  Brighton 

Summit  of  Arbutus  avenue  one-fourth  mile  south  of  Brighton, 
crossing  the  east  end  of  the  I'innacle  hills  esker 

Top  of  esker  about  50  rods  west  of  last 

Top  of  esker  one  third  mile  farther  west 

Depression  close  southwest  of  last 

Highest  point  of  Cobb's  hill,  one-third  mile  farther  W.  S.  \V.. 

Top  of  esker  about  40  rods  westward 


the  Sf;i. 

436 

508 
5>6 

500 
460 

4S0 

570 
652 

59° 
663 

60S 


^^J3\  Ul'HAM  — KSKliRS    NKAK    kOCHESTKR,    N.   Y. 

Feet 

IntL'.-sectioii  of  ^[()nroe  and  Highland  avenues,  at  Mrs.  W.  H. 
Cobb's  residence,  immediately  soutii  of  last 

The  Pinnacle,  one-half  mile  farther  west 

Summit  of  Pinnacle  avenue,  crossing  the  esker  one-third  mile 
farther  west 

Top  of  esker  in  Highland  park,  at  the  Memorial  Pavilion... 

Mt.  Hope  reservoir,  water  surface 

Summit  of  South  avenue 

Summit  of  Mt.  Hope  avenue. 

Highest  portions  of  the  esker  in  .Mt.  Hope  cemetery,  about. 

Crest  of  morainic  ridge  extending  westward  as  a  continuation 
of  the  Pinnacle  hills,  where  it  is  cut  by  the  Cenesee  Val- 
ley branch  of  the  New  York,  Lake  Erie  &  Western  rail- 
road  

Same,  on  east  bank  of  the  Centsee  river 

Same,  west  of  the  river,  at  the  Rapids  cemetery  and  onward.. 555- 

(ienesee  river  above  the  State  dam,  near  the  foregoing 

At  foot  of  this  dam 

At  the  Clarissa  street  bridge 

At  the  Court  street  bridge 

At  the  Andrews  street  bridge 

Upper  falls,  toj)  of  rock,  476  ;  water  in  ordinary  stage  at 

brink  and  foot  of  the  full  ,,, 

■        '" " -    t/o' 

Above  and  below  the  Middle  falls -,■,,. 

At  mouth  of  Deep  Hollow  creek  and  brink  of  Lower  falls 

At  foot  of  Lower  falls 

.    At   the   steamboat  landing,  about  one  mile  north   of  the 
last,  on  the  level   of  lake  Ontario 

Seneca  Park  bridge,  spanning  the  gorge  close  below  the  Lower 
falls 

Highest  ground  at  the  Rochester  University 

Canal  and  railroad  at  Pittsford,  about 

Irondequoil  river  under  the  viaduct  of  the  Erie  canal,  about 

Turk's  hill,  a  station  of  the  U.  S.  Lake  Survey  triangulation, 
near  the  south  line  of  Perinton  township,  about  12  miles 
southeast  from  the  Pinnacle  hills 

Rush  reservoir  of  the  Rochester  Water  Works,  9  miles  south 
of  the  Mt.  Hope  reservoir 

Hemlock  lake  (ma.ximum  deinli,  87  feet),  source  of  the  Roch- 
ester water  supply,  19  miles  from  tb  -  Rush  reservoir 


189 

above 
sea. 

544 
749 

5S3 
650 

634 
r,,7 

622 
675 


583 
559 
-560 

508 
504 
50- 
493 
484 

-3-^7 
-34'^ 
345 
^5' 

247 

460 
520 
4O0 
400 


928 

753 
S98 


IQO 


ROCHESTER    ACADEMY    OK    SCIENCE. 


[Jan.  9, 


ESKERS    IN    PiTTSFORU. 

From  2i^  to  3  miles  southeast  of  Brighton,  the  New  York  Central 
railroad  makes  a  long  cut  through  the  northern  end  of  a  second  esker 
series,  which  takes  a  course  approximately  at  right  angles  with  that 
of  the  Pinnacle  hills.  Beginning  close  south  of  Allen's  creek,  in  the 
southwest  corner  of  Penfield  township,  this  belt  of  kames  and  eskers 
runs  south-southeasterly  through  the  east  half  of  Pittsford  and  about 
a  mile  into  the  southwestern  corner  of  Perinton,  terminating  in  a  sand 
l^lateau,  which  abuts  upon  the  western  base  of  the  prominent  Turk's 
hill  range  of  drumloid  drift.  The  length  of  this  Pittsford  esker  series 
is  about  seven  miles. 

In  its  northern  third,  extending  from  Allen's  creek  southward  to 
about  a  mile  east  of   Pittsford  village,  the  width  of  this   belt  varies 
mainly  from  a  half  mile  to  fully  one  mile,  and  it  consists  of  a  princi- 
pal broad  north  to  south  esker  ridge,  becoming  narrower  and  inter- 
rupted southward,  with  a  considerable  lateral  expansion,  especially  on 
the  east,  in   kames,  or  short   ridges,  mounds  and  hillocks,  all   being 
composed  of  sand  and  gravel,  with  infrequent  enclosed  boulders.    I'he 
cut  for  the  railroad  is  about  a  half  mile  long  and  50  feet  deep.      Its 
greater  part  is  yellow  sand,  nearly  horizontal  in  stratification,  except- 
ing at  the  margins,  where  the  bedding  is  more  irregular,  prevailingly 
dipping  downward  like  the  surface  slopes.     In  this  sand  are  occa- 
sional thin  gravelly  layers,  but  these  are  nowhere  conspicuous.     Very 
rare  embedded  boulders  were  seen.      Only  two,  which  were  respect- 
ively about  3  and  5  feet  in  diameter,  were  exposed  in  the  section  at 
the  time  of  my  visit,  and  scarcely  a  half  dozen  in  total  lie  at  the  foot 
of  the  banks  on  both  sides  of  the  railroad.      The  basal  part  of  this 
section,  however,  for  about  an  eighth  of  a  mile  west  from  its  center, 
consists  of  coarse  gray  gravel,  containing  very  closely  packed  gravel 
stones  and    cobbles  up  to  6  or  8  inches  in  diameter,   but  no  larger 
boulders.     On  the  north  side  of  the  excavation  the  gravel  reaches  to 
a  height  of  about  20  feet  above  the  track,  and  displays  a  very  distinct 
anticlinal  stratification. 

About  i>^  miles  southeast  from  this  ra-'road  cut,  a  small  excava- 
tion for  the  passage  of  a  north  to  south  road  through  a  kame  deposit, 
chiefly  of  sand,  near  the  east  line  of  Pittsford  and  the  east  border  of 
the  esker  and  kame  belt,  reveals  a  boulder  3^^  feet  in  diameter, 
embedded  10  feet  below  the  surface.  Beneath  and  above  the  boulder, 
the  stratification  of  the  sand  and  gravel  is  contorted  and  curved,  in 
conformability  with  the  outline  of  the  rock  mass. 


i893] 


UPHAM— ESKERS    NEAR    ROCHESTER,    N.  Y. 


191 


After  an  interruption  or  gap  about  40  rods  in  length,  the  more 
southern  portion  of  the  series,  from  a  point  about  a  mile  east-south- 
east of  Pittsford  village  to  its  termination  about  a  mile  southeast  and 
sou.n  of  the  village  of  Bushnell's  Basin  in  Perinton,  is  well  described 
as  follows,  by  Mr.  Charles  R.  Dryer,  in  a  paper  which  also  treats  of 
the  Pinnacle  hills.  Irondequoit  bay,  and  the  massive  hill  ranges  of  till 
south  of  Pittsford  and  Fairport  (').  Mr.  Dryer,  following  the  early 
usage  of  the  term  kaine,  applies  it  to  the  narrow  esker  ridge,  with  steep 
slopes  and  sharp  crest,  which  he  describes  one  to  three  miles  south- 
east of  Pittsford,  succeeded  in  the  next  mile  or  more  by  a  sand  plain  or 
plateau. 

"  The  north  end  is  a  sharp  ridge  of  very  coarse  gravel,  fifty  feet  in  height, 
one  mile  long,  and  in  shape  like  a  rude  fish-hook.  It  is  separated  from^he 
southern  portion  by  the  channel  of  Irondec|uoit  river,  which  has  cut  the  kame 
completely  in  two.  In  the  southern  portion  the  gravel  is  overlaid  by  fifty  feet 
of  fine  sand  which  spreads  out  toward  the  southeast  in  a  sheet  a  mile  or  more 
m  width.  This  kame  forms  a  dam  across  the  valley,  complete  except  for  an 
interval  of  less  than  one-fourth  of  a  mile  on  its  western  side.  The  Erie  canal 
avails  Itself  of  this  kame  to  cross  the  valley  and  by  a  fifty-foot  embankment 
restores  what  probably  once  existed  as  a  natural  feature.  South  of  the  kame 
the  valley  is  as  level  as  a  floor  for  three  miles  up  the  stream  and  was  evidently 
once  the  site  of  a  lake  whose  waters  were  held  back  by  the  kame  as  a  dam." 

Relationship  to  Drumlins  and  Terminal  Moraines  on  the  soi//h.—To 
understand  the  history  of  the  recession  of  the  ice-sheet  in  this  region  and 
of  the  accumulation  of  its  drift,  it  is  needful  for  us  to  take  for  a  moment 
a  somewhat  broad  viev  southward.  Beginning  within  a  half  mile  south 
of  Pittsford,  drumlins  are  admirably  developed  upon  an  area  extend- 
ing six  or  seven  miles  to  the  south,  into  the  northwest  part  of 
Mendon.  They  also  form  the  crests  of  a  massive  drift  ridge  which 
stretches  from  Fairport  south  to  Victor,  culminating  in  Turk's  hill  ; 
and  beyond  a  depression,  through  which  the  railroad  from  Rochester 
to  Canandaigua  passes,  similar  massive,  drumlin-crowned  highlands 
extend  from  Victor  several  miles  to  the  south  and  southwest.  These 
highlands  appear  to  me  referable  to  the  class  of  drumlins,  rather  than 
to  that  of  terminal  moraines  marking  the  outlines  of  the  ice-front  at 
any  stage  of  temporary  halt  in  its  general  retreat.  Eastward  from 
this  region,  drumlins  occur  in  extraordinary  abundance  for  a  distance 
of  60  miles,  to  the  vicinity  of  Syracuse  ('). 

wi,h*'nap'!'A^,ri:,''8^'.  ^'"'°^''  °^  ''"'  I'""'"-'"""  R'^S-"-  Am.  Gcolo^nst,  Vol.  V,  pp.  .0.-.07, 

V  /V'  oJ'-  '"''"T!?'  "7'"=  Parallel  Hills  of  Western  New  York,"   Trans    N   V  Acad    of  Sri 
\ol.    ,  .88.,  pp.  ,8-So;  Annals,  d,..,  Vol.  H,  pp.  24^-^66,  with  map.  '  ^■^■^^'''^-  of  Sci., 

y^A^lAx:'^':^^^^^':^.'^'''''''^'''^''^''  '^*-'«'-"  '"■  -^■•-■"-  Vork,"Am.  Jour.,  Sci.,  III. 

362,  De",''"?S   !'''"'""    '^""''''■''"''''^  Accumulation  of  Drumlins."  Am.  Geologist,  Vol.  X,  pp.  33^- 


192 


ROCHESTER    ACADKMV    OK    SCIENCE. 


[Jan.  9, 


Between  35  and  60  miles  smith  of  Rochester,  conspicuous  termi- 
nal moraines  run  approximately  from  west  to  east,  as  described  and 
mapped  by  Professor  T.  C.  Chambcrlin  (').  On  the  meridian  of 
Rochester  these  moraines  are  somewhat  interblended,  fragmentary, 
and  irregular  in  their  development  upon  a  width  of  nearly  25  miles 
from  the  southern  ends  of  Conesus  and  Hemlock  lakes  southward  lo 
the  vicinity  of  Hornellsville.  Farther  to  the  east,  for  a  distance  of 
about  150  miles,  to  the  Catskill  mountains  and  the  Mohawk  river, 
they  are  more  distinctly  developed  as  two  morainic  belts,  of  which  the 
southern  one  is  traced  in  a  slowly  curving  course,  convex  toward  the 
south,  along  the  valleys  of  the  Canisteo,  Tioga  and  upper  Susque- 
hanna rivers,  while  thr  northern  one  passes  in  a  more  sharply  curved 
and  lobate  course  by  the  south  ends  of  the  Finger  lakes  to  Ilion  and 
Herkimer  on  the  Mohawk.  In  the  valleys  extending  southward  from 
the  heads  of  the  larger  Finger  lakes  the  thickness  of  the  northern 
moraine  a[)pears  to  be  several  hundreds  of  feet,  and  in  the  case  of 
Seneca  lake  perhaps  inore  than  1,000  feet ;  but  on  the  intervening 
plateaus  the  thickness  of  the  morainic  drift  is  comparatively  insig- 
nificant, averaging  probably  no  more  than  25  to  50  feet  upon  widths 
varying  from  one  to  two  or  three  miles. 

A  more  distant  moraine,  however,  lying  on  and  near  the  bound- 
ary of  the  glacial  drift,  extends  from  the  vicinity  of  Salamanca,  N.  Y., 
east-southeasterly  to  the  Delaware  river  at  Belvidere,  N.  J.,  and  to 
Staten  Island,  the  Narrows,  and  Long  Island.  This  moraine, 
described  in  Pennsylvania  by  Professors  Lewis  and  Wright,  (-)  passes 
about  100  miles  south  of  Rochester. 

Relationship  to  Glacial  Movonents. — The  currents  of  the  ice-sheet 
flowed  perpendicularly  toward  its  boundaries  and  marginal  moraines, 
that  is,  to  the  south  or  somewhat  west  south  for  the  region  about 

Rochester  and  Pittsford  ;  but  during  the  recession  of  the  ice  from 
that  area,  its  currents  were  in  some  portions  deflected  much  to  the 
west,  because  of  more  rapid  melting  of  the  ice  on  that  side  and  con- 
sequent indentations  or  embayments  in  its  border.  This  faster  melt- 
ing on  the  west  was  probably  at  first  due  in  large  part  to  the  laving 
action  of  the  glacial  Lake  Warren,  which  extended  from  the  western 
part  of  the  basin  of  Lake  Ontario  over  the  upi)er  Laurentian  lakes, 
outflowing  at  Chicago  to  the  Des  Plaines,  Illinois,  and  Mississippi 
rivers  ;  and  in  the  later  stage  of  the  glacial  recession  when  the  Roch- 


M.i     riiird    Annual   Report   of    the  U.S.  duol.  Survey,  fur   1S81-S2,  pp.  ^551-^60,  with  Plate 
XXXIII. 

U'.l     Report  Z,  Second  Geol.  Survey  of  Pennsylvania. 


1 893- J 


Ul'HANr — ESKERS    NEAR    ROCHESTER,    N.   Y. 


193. 


ester  and  Pittsford  eskers  were  formed,  the  ice-melting  was  likewise 
promoted  by  the  incipient  Lake  Iroquois,  outflowing  by  Rome  to  the 
Mohawk  and  Hudson. 

According  to  notations  of  glacial  striiij  by  Chamberlin,  Gilbert, 
and  Dryer,  their  courses  are  as  follows  :  near  the  northeast  corner  of 
the  city  of  Rochester,  S.  S.  W.  to  S.  W. ;  near  the  southwestern  bound- 
ary of  this  city,  S.  W.  to  W.  S.  W.;  and  in  (Ireece,  the  next  township 
northwest  of  Rochester,  four  courses,  intersecting  or  on  contiguous 
rock  exposures,  S.  S.  E.,  S.  S.  W,,  S.  W.,  and  W.  Thesouthward  courses 
are  doubtless  somewhat  earlier  than  those  running  to  the  south- 
west and  west,  which  belong  to  the  short  time  when  the  glacial  cur- 
rents were  deflected  during  the  departure  of  the  ice.  Upon  all  the 
region  of  the  Finger  lakes  the  glacial  striation  is  approximately  from 
north  to  south,  in  parallelism  with  these  lakes  and  the  intervening 
ridges  and  plateaus.  On  the  north  the  grand  ice  currents  over  the 
^'rovince  of  Ontario  moved  mainly  southward,  with  convergence 
from  the  southern  part  of  (Georgian  l^ay  southeasterly,  and  from  Mon- 
treal and  the  upper  St.  Lawrence  southwesterly,  toward  the  basin  of 
Lake  Ontario  and  the  great  re-entrant  angle  of  the  glacial  border  at 
Salamanca  in  southwestern  New  York. 

The  trends  of  eskers  and  drumlins  testify  of  the  directions  of  the 
currents  of  the  ice-sheet  as  trustworthily  as  the  courses  of  glacial 
striation  on  the  bed-rocks,  with  which  the  esker  and  drumlin  ridges 
are  parallel.  Eoth  these  classes  of  drift  accumulations,  however,  were 
formed  near  the  border  of  the  ice  during  its  recession  at  the  close  of 
the  (llacial  period  ;  and  they  consequently  often  record  local  deflec- 
tions of  the  glacial  currents  caused  by  unequal  rates  of  melting  and 
the  resultant  sinuosities  of  the  ice-front.  The  IMttsford  esker  series, 
trentling  south-southeast,  is  nearly  parallel  with  the  general  move- 
ment of  the  ice-sheet,  both  during  the  time  of  its  maximum  extent 
and  thickness  and  during  the  decadence  ;  but  the  Pinnacle  hills,  trend- 
ing west- southwest,  show  that  a  considerable  local  indentation  or 
embayment  in  the  waning  ice-border  there  turned  its  currents  much 
to  the  west  from  their  former  course. 

Proi!A1',i.e  Origin  of  these  Eskers. 


Although  these  two  esker  series,  lying  only  a  few  miles  apart, 
differ  about  90^  in  their  trends,  they  were  p'-obably  formed  at  the 
same  time  or  one  very  soon  after  the  other,  a:  >  "ght  happen  by  diver- 

ij,  Pkuc.  Roch.  Acad,  ok  Sc,  Vol..  j,  April,  1893. 


194 


ROCHESTER    ACADEMY    OK    SCIENCE. 


[Jan.  9, 


sion  of  a  glacial  river  from  one  avenue  into  another  near  its  point 
of  discharge  from  the  ice-sheet.  Each  series  seems  to  be  attributable 
to  deposition  in  the  ice-walled  channel  of  a  stream  of  water  flowing 
down  from  the  surface  of  the  melting  ice-sheet,  where  the  gravel  and 
sand  had  been  gathered  from  the  previously  er.glacial  drift  that  had 
been  exposed  by  ablation  as  a  superglacial  stratum.  Near  their 
mouths,  or  places  of  discharge  to  the  land  surface,  these  rivers  appear 
to  have  flowed  in  valleys  or  gorges  inclosed  by  unmelted  plateaus  of 
the  ice-margin,  upon  which  much  drift  rested.  In  some  sections  of 
our  drift  formations,  as  of  Third  and  Fourth  Cliffs  in  Scituate,  Mass., 
which  are  partially  eroded  drumlins  on  the  shore  of  the  ocean,  thick 
beds  of  stratified  gravel  and  sand  are  found  which  were  undoubtedly 
laid  down  by  subglacial  streams  (').  But  such  beds  formed  under  the 
ice-sheet  are  rare  in  most  parts  of  the  country,  and  the  eskers  here 
described  and  all  others  which  have  come  under  my  examination  of 
extensive  areas  in  New  England,  and  in  Minnesota,  northern  Iowa, 
the  Dakotas,  and  Manitoba,  I  believe  to  have  been  deposited  in  ice- 
walled  channels  open  above  to  the  sky. 

Before  proceeding  to  consider  more  in  detail  the  structure  and 
materials  of  these  eskers  in  their  bearing  on  this  view  of  their  mode  of 
accumulation,  it  will  be  desirable  to  notice  former  expressions  of  opinion 
as  tc  the  origin  of  the  Pinnacle  hills.  The  earliest  reference  to  this 
esker  is  by  James  Hall,  in  his  report  on  the  Fourth  Geological  Dis- 
trict of  New  York,  published  in  i<S43.  In  pages  323  and  324  he  gives 
a  flgure  and  description  of  the  section  where  the  ridge  is  intersected 
by  Monroe  avenue.  "The  gravel,"  Professor  Hal!  remarks,  "con- 
sists principally  of  waterworn  fragments  of  the  Niagara  limestone,  on 
which  the  whole  deposit  rests,  and  of  the  sandstones  anfl  limestones 
on  the  north.  There  are  some  boulders  of  the  limestone,  from  two 
to  four  feet  in  diameter,  worn  perfectly  smooth,  or  often  striated  with 
shallow  grooves  ;  and  from  the  fact  that  this  is  the  subjacent  rock,  they 
have  received  their  rounded  forms  and  smooth  surfaces  from  attrition 
near  the  spot  where  we  now  find  them."  When  this  was  written,  the 
glacial  theory  of  Agassiz  had  been  published  only  a  few  years,  and 
was  not  apprehended  by  Hall  with  such  clearness  as  to  seem  adetjuate 
to  account  for  this  and  our  other  drift  deposits.  It  was  observed  that 
in  this  section  "  nearly  all  the  strata  dip  towards  the  west,"  whence 
it  was  concluded  that  "  the  accumulation  doubtless  took  place  from 


(i.l     Proceedings  of  the  Boston  Society  of  Niitural   History,  Vol.  XXIV,  iSS,j.  lU).  "S-2j-  ; 
Vol.  XXV,  1891,  pp. -..28-242.  '      "      ^' 


1 893- J 


UI'HA.M — ESKKRS    NKAR    ROCHESTER,    X.   Y. 


195 


this  direction,  from  the  heaping  of  the  coarse  gravel  upon  the  fine 
sand." 

Mr.  Charles  R.  Dryer,  in  the  article  before  cited,  calls  both  the 
Pinnacle  hills  and  the  I'ittsford  series  kanies,  implying  their  deposi- 
tion in  the  channels  of  glacial  rivers.  He  especially  notices  that  on 
the  area  where,  if  prolonged  to  the  northeast  and  north,  they  would 
intersect,  the  valley  of  Irondequoit  bay  has  been  apparently  filled 
with  stratified  sand  and  gravel  to  a  height  of  150  feet  or  more  above 
the  lake,  as  indicated  by  narrow  terraces  at  such  height  left  on  each 
side  of  the  bay.  The  level  of  the  glacial  Lake  Iroquois  during  a  late 
stage  of  its  history,  according  to  Mr.  Gilbert,  sank  here  considerably 
below  the  shore  of  Lake  Ontario,  and  the  depth  of  the  Irondequoit 
bay  suggests  that  the  depression  of  this  southern  part  of  the  glacial 
lake,  permitting  erosion  of  the  former  plain  of  modified  drift  in  the 
Irondequoit  valley,  reached  at  least  80  feet  beneath  the  present  water 
level. 

The  discussion  concerning  the  origin  of  the  Pinnacle  hills  after 
the  excursion  to  them  last  summer  by  members  of  Section  E  of  the 
American  Association  was  opened  by  Mr.  Gilbert,  who  drew  on  the 
blackboard  a  sketch  map  of  the  esker  series  and  the  region  about  it 
and  called  attention  to  the  narrowness  of  the  east  and  west  belts  of 
outcrop  of  the  several  geologic  formations.  The  Niagara  limestone, 
occupying  a  belt  that  ranges  from  2  to  7  miles  in  width  through  this 
part  of  New  York,  underlies  the  Pinnacle  hills  and  much  of  the  city 
of  Rochester.  Next  northward  the  Clinton  formation  has  a  similar 
width,  and  beyond  this  the  Med'na  sandstone  outcrops  on  a  somewhat 
wider  belt  which  adjoins  Lake  Ontario.  Each  of  these  formations 
and  the  Archaean  rocks  of  Canada  are  represented  in  the  gravel  ?nd 
boulders  of  this  hill  range,  and  it  is  especially  notable  that  usually 
the  Niagara  limestone  is  very  plentiful,  both  as  gravel  and  as 
boulders,  which  vary  in  size  up  to  ten  feet  in  diameter.  Evidently 
this  limestone  drift  can  have  been  transported  only  a  few  miles,  and 
its  occurrence  in  the  highest  portions  of  the  Pinnacle  hills  must  be 
taken  into  account  in  inquiring  how  they  were  accumulated,  for  which, 
however,  Mr.  Gilbert  had  not  framed  any  complete  and  detailed 
explanation. 

Professor  G.  F.  Wright  and  Mr.  C.  W.  Hayes  spoke  of  their  own 
observations  and  those  of  Prof.  I.  C.  Russell  on  glaciers  in  Alaska, 
where  much  superglacial  drift  is  exposed  on  the  wasting  borders  of 
the  ice-fields  and  portions  of  it  are  washed  away  by  rains  and  streams, 
which   in  most  cases  carry  it  finally  into  crevasses   and  subglacial 


IQf) 


RDCHESTKK    academy    (IF    SCIENCE, 


f  Ian.  9 


water  courses,  like  those  of  the  N'ahtse  river  and  Fountain  stream 
described  by  Russell  as  llowing  out  from  beneath  the  Malaspina 
jflacier.  In  these  subglacial  channels  the  streams  must  be  building  up 
eskers,  while  gently  sloping  gravel  and  sand  plains  are  being  deposited 
by  the  silt-laden  waters  in  their  course  from  the  ice  front  to  the  sea  ('). 

Professor  K.  \V.  Claypole  drew  a  section  of  the  marginal  portion 
of  the  ice-sheet,  showing  how,  in  his  opinion,  the  Pinnacle  lulls  were 
formed  by  a  stream  which  gathered  drift  from  the  melting  ice  surface, 
and  then  fell  through  a  crevasse  and  deposited  the  sand,  gravel,  and 
boulders  in  a  tunnel  under  the  ice. 

Following  these  speakers,  I  remarked  that  the  absence  of  any 
covering  of  till  upon  the  top  and  slopes  of  this  esker,  such  as  must 
have  fallen  upon  it  from  the  englacial  and  suj)erglacial  drift  of  its  roof 
of  ice  if  it  were  formed  in  a  subglacial  tunnel,  leads  me  to  believe 
that  its  stream  was  wholly  superglacial,  and  that  the  esker  was  depos- 
ited in  a  deep  ice-walled  gorge,  open  above  to  the  sky,  eroded  in  the 
border  of  the  ice-sheet  by  the  melting  action  of  the  running  water. 

The  purpose  of  the  present  essay  will  be  completed  by  more  fully 
considering  the  probable  manner  of  transportation  of  the  many  boul- 
ders found  in  some  portions  of  the  gravel  and  sand  of  the  Pinnacle 
hills,  the  relationship  of  this  esker  to  the  lower  morainic  ridge  con- 
tinuous from  it  westward,  the  abrupt  eastward  ending  of  the  Pinnacle 
hills  range,  and  similar  features  of  the  Pittsford  esker  series,  with  the 
incpiiry  constantly  in  mind  whether  these  features  support  the  view 
that  these  eskers  were  derived  from  previously  englacial  drift  and 
accumulated  in  superglacial  channels.  It  will  be  needful  at  the  same 
time  to  consider  the  drainage  from  the  ice-border  in  its  tlations  to 
the  glacial  Fake  ^\'arren  and  to  the  beginnings  of  Fake  Iroquois. 
Feyond  this  we  ought  t'^  'earn,  if  possible,  whether  the  same  expla- 
nation is  generally  applicable  to  eskers  in  other  regions. 

The  leading  reason  for  our  special  interest  in  the  Pinnacle  hills  is 
the  demonstrably  near  sources  of  their  Niagara  limestone  boulders, 
which  have  been  transported  only  a  few  miles  and  yet  were  uplifted 
at  least  loo  to  200  feet  into  the  ice-sheet  from  an  approximately  plain 
country.  Here  we  have  a  demonstration  of  the  competency  of  the 
glacial  currents  to  gather  drift  into  the  lower  part  of  the  ice-sheet 
from  a  u'^-^rly  flat  area,  and  we  may  understand  how  this  takes  place 
by  the  differential  movements  of  the  ujiper,  middle  and  lower  portions 
of  the    ice.       Upon    a    belt   of    the   ice-sheet    extending   many  miles 


(ii.     I'lir  description  (if  tlic  present  process  tif  fdrmatiim  of  eskcrsanil  sand  plains  l)y  rivers 
■{iissell's  paper  on  "  ^■ 
iUi  map,  Marcli,  iSiyj 


of  tlie  Malas])ina  k''"!'-''',  see  Kiissell's  paper  on  "  Mt.  St.  Klias  and  its  Glaciers,"  Am.  Jour.  Sci,. 
Ill,  Vol.  XI.III,  pp.  iiy-jS..,  u'  ■  


'893-1 


UI'HAM — K.SKKKS    NKAK     KdCIIb.STER,    N.    V. 


'97 


inward  from  the  retreating  margin,  its  surface  had  a  considerable 
slope,  so  that  the  upper  currents  of  the  ice,  unsupported  on  the  outer 
side,  would  move  much  faster  than  its  lower  currents  which  were 
impeded  by  friction  on  the  land.  'I  here  would  be  accordingly  within 
tills  belt  a  strong  tendency  of  the  ice  to  flow  outward  with  somewhat 
curved  currents,  tending  first  to  carry  the  onwardly  moving  drift 
gradually  upward  into  the  icesheet,  anil  later  to  bear  it  downward 
aiHl  deposit  it  )iarlly  beneath  the  edge  of  the  ice  and  partly  along  the 
ice  boundary.  The  Niagara  bouklers,  and  others  from  the  Clinton 
and  Medina  formations  farther  north,  having  been  borne  upward  as 
englacial  drift  to  a  greater  altitude  than  the  I'innacle  hills,  were 
exposed  on  the  surface  of  the  ice-sheet  by  its  ablation  and  were 
swept  by  torrents  bearing  ice  rafts,  or  probably  sometimes  by  ava- 
lanches, into  the  river  channel.  Their  great  profusion  in  certain 
parts  of  this  esker  implies  unusual  abundance  in  and  upon  the  contig- 
uous portions  of  the  ice-sheet,  which  may  iiave  resulted  from  conver- 
gent glacial  currents  and  periiaps  from  a  temporary  re-advance  of  the 
thicker  tract  of  the  ice,  massing  its  superglacial  drift  stratum  in  a 
way  analogous  with  the  accumulation  of  terminal  morainic  hills,  which 
often  are  equally  charged  with  boulders. 

The  morainic  ridge  continuing  \vestward  from  the  Mt.  Hope 
cemetery  seems  probably  to  have  been  formed  along  the  margin  of 
the  ice,  on  the  northern  side  of  a  re-entrant  angle  or  embayment  into 
which  the  glacial  river  dei)ositing  the  esker  of  the  Pinnacle  hills 
debouched.  Close  south  of  this  ridge,  a  brick  yard  beside  the  Ihiftalo, 
Rochester  \:  Pittsburgh  railroad  works  the  stratified  clay  which  the 
river  discharged  into  the  shallow  glacial  lake  of  the  embayment. 

Finding  so  abrupt  an  end  of  this  esker  at  Brighton,  we  are  con- 
strained to  believe  that  the  powerful  riverby  which  it  was  accumulated 
suddenly  ceased  to  flow  here.  The  neighboring  I'ittsford  esker  appar- 
ently shows  the  site  of  the  new  glacial  channel,  previously  the  course 
of  some  smaller  stream,  which  then  becane  the  main  avenue  of  drain- 
age from  the  rapidly  melting  ice-fields  of  this  region.  Put  when  the 
Pittsford  esker  had  gradually  grown  in  its  length  from  the  west  flank 
of  the  Turk's  hill  range  northward  to  the  present  site  of  Allen's  creek, 
the  glacial  river  which  formed  it  was  again  diverted  ;  or  more  prob- 
ably thenceforward  it  emptied  into  a  marginal  lake  so  broad  and  dee|i 
that  no  distinct  esker  was  made,  the  gravel  and  sand  being  then  laid 
down  in  the  valley  which  now  holds  Irondecpioit  bay. 

If  the  eroded  drift  from  the  area  north  of  the  I'innacle  hills  was 
carried  upward  by  glacial  currents  having  an  average  ascent  of  one 


198 


UOCHF.SIER    Al.ADK.MY    OK    SCIKNCE. 


[Jail.  9, 


degree,  it  would  rise  within  one  mile  9:;  feet  and  within  two  or  three 
miles  would  be  higher  than  tlu-  tops  of  these  hills.  Currents  ascend- 
ing at  this  rate,  or  even  two  or  three  degrees  or  more,  may  very  prob- 
ably  have  existed  in  the  lowest  part  of  the  ice  sheet,  on  account  of  the 
acceleration  of  its  upper  currents,  within  distances  from  20  to  50 
miles  or  more  back  from  its  boundary,  liy  these  currents  much  drift 
eroded  from  the  land  surface  would  be  gradually  incorporated  in  the 
comparatively  sluggish  lower  part  of  the  ice,  reaching  altitudes  100 
to  1,000  feet  above  the  ground  within  a  few  miles  from  its  sources. 

It  is  also  to  be  remarked  that  the  rounded  or  at  least  subangular 
forms  of  the  greater  part  of  the  pebbles  and  small  rock  fragments  in 
the  esker  gravel  do  not  necessarily  imply  wearing  by  the  stream  dur- 
ing a  long  transportation.  Daubree  placed  angular  fragments  of 
granite  and  cjuartz,  ranging  from  the  si^e  of  one's  fist  to  that  of  a  hazel 
nut,  with  water  in  slowly  revolving  cylinders  and  found  that  they 
became  perfectly  rounded  when  the  revolutions  amounted  to  25  kilo- 
meters or  about  15  miles.  (')  Within  a  third  of  this  distance  probably 
some  of  the  fragments  had  been  well  nninded,  and  in  a  less  distance 
nearly  all  would  be  worn  to  subangular  forms. 

Many  features  of  the  modified  drift,  comprising  glacial  flood 
plains,  eskers  and  kames,  show  that  the  melting  of  the  ice-sheet  at  the 
close  of  the  ("dacial  period  was  mostly  very  rapid.  In  the  vicinity  of 
Rochester  it  was  hastened  by  the  laving  action  of  the  glacial  lakes  on 
its  southern  border.  Lake  Warren  had  formed  a  beach  which  extends 
to  the  south  side  of  the  east  end  of  Lake  Erie,  where  its  altitude  is 
860  feet  above  the  sea.  (')  At  the  time  of  formation  of  the  Pinnacle 
hills  and  Pittsford  esker  series,  the  ice-border  in  New  York  appears  to 
have  receded  so  far  that  the  water  of  the  uppei  Laurentian  lakes  was 
no  longer  held  up  to  the  level  of  Lake  Warren,  which  had  outflowed 
at  Chicago,  and  avenues  of  drainage  seem  already  to  have  been  opened 
eastward  along  the  ice-border  past  the  northern  ends  of  the  Finger 
lakes  to  the  Mohawk  valley.  Undoubtedly  the  deposition  of  these 
esker  gravel  and  sand  beds  took  place  above  the  level  of  such  fring- 
ing lakes,  which  from  the  C.enesee  and  Irondequoit  basins  could  have 
no  place  of  outflow  eastward  lower  than  by  the  way  of  Victor  and 
Mud  creek.  The  divide  at  Victor  is  somewhat  higher  than  the  gen- 
eral surface  on  which  these  eskers  lie  ;  hence  it  seems  probable  that 
when  the  esker  beds  were  laid  down  in  their  ice-walled  channels  a 
depth  of  some  100  feet,  more  or  less,  of  ice  still  remained  unmelted 


1 1  )     Ktiuics  Svnlhetiqucs  de  GiMilotcie  ExpiTimentale  1879,  pp.  248-250. 
(2.)    Bulletin.'G    S.  A.,  V<>\.  II,  pp.  25S-265  ;  \  ol.  Ill,  pp.  4^4-4^7- 


'■^93. 1 


UPHAM— K.SKERn    NKAK    ROCHESTER,    N.   V. 


199 


beneath  them.  In  like  manner  I  have  shown  that  certain  eskers  in 
New  Hampshire  and  Manitoba  were  underlain  by  ice  at  the  time  of 
their  accumulation  and  by  its  meltinj;  away  were  afterward  allowed  t<, 
hink  to  the  land.  (') 

.ViM'Mc  A  riiiN  ()!•    riii>  K.Mi.AN  A  Hon    lo  Eskers  elsewhere. 

If  eskers  were  subglacial  deposits,  we  should  e.xpect  them  to  be 
often  covered  wholly  or  partly  with  the  enyiacial  drift,  as  bcuUders 
and  loose  deposits  of  till,  which  would  be  permitted  to  fall  upon  them 
when  the  ice-roof  was  melted  away.  Such  a  roof  would  be  iiKjre  or 
less  overspread  with  the  drift  that  had  been  c(jntained  in  the  higher 
portions  of  the  icesheet  and  was  exposed  on  its  surface  by  ablation. 
Sections  indeed  are  occasionally  found,  where  subylacial  beds  of 
modified  drift  have  become  covered  by  sub,t,^lacial  and  euglacinl  till  ;  (') 
but  these  usually  differ  widely  in  their  character  from  the  torrential 
esker  and  kame  deposits,  which  very  rarely  contain  or  bear  upon  their 
surface  any  considerable  abundance  of  boulders  or  other  drift  mate- 
rials that  have  not  evidently  been  transported,  worn,  and  assorted  by 
water.  In  nearly  all  the  localities  where  I  have  observed  boulders  or 
masses  of  till  imbedded  within  eskers  or  lying  on  their  surface,  the 
most  probable  explanation  of  their  derivation  has  been  by  falling 
Irom  the  enclosing  ice- walls  of  channels  ojjen  U>  the  sky,  or  by  being 
brought  while  f"ozen  in  ice-lloes.  ('')  At  only  one  place,  in  Dover, 
N.  H.,  1  have  found  a  portion  of  an  esker  covered  with  a  deposit  of 
boulders  and  till  which  may  have  fallen  from  a  melting  ice  roof, 
th(jugh  another  interpretation  seems  to  me  preferable.  (*) 

A  different  view  is  taken  by  Professor  W.  M.  Davis,  who  regards 
certain  eskers  in  the  vicinity  of  Auburndale,  Mass.,  which  1  have 
repeatedly  examined  with  him  and  other  glacialists,  as  probably  of  sub- 
glacial  origin.  (')  These  eskers  I  think  to  have  been  formed  in  ice- 
walled  channels,  (jpen  above  and  underlain  by  a  slight  depth  of  ice 
Extending  southward  from  them  are  associated  sand  plains  or  plateaus, 
deposited  just  outside  the  ice  front  by  the  streams  which  produced  the 
esker  ridges.     Professor  Davis  describes  a  backwardly  dipping  strati- 

II.)  (iculciKV  I't  Nl'W  lhiin|)shiie.  Vul.  Ill,  10713,141.  1.7,11''.  (ie.jl.  and  N.it.  lli-.l.  Survey  of 
C.uiaila,  Annual  Riiiort,  iua  -.crios,  Veil.  IV,  for  iSSKS'i,  pp.  .ij-^i  E. 

i_-.i  (;eolni;yot  N.  H.,  VmI.  III.  pp.  i..S,  1  ii  1 -,7,  -s,,  2..,i.  OtoLiintl  Nat.  Mini.  Survey  ot  Minne- 
sota, kiululi  Animal  Krp..rt,  for  17,.  pp.  11 ,,  114  ;  Ein.il  Rep^rl,  \'ols.  I  and  II.  I'roceedingb  of 
the  Moston  Soi.-jety  of  Natur.il  History,  \'ol.  XXlV,  i.i.-f),  pp,  -ni-s,  21.7-'). 

t  i.l  (ieoloyy  of  N.  H,,  Vol.  Ill,  pp.  4;,  4'%  hs,  if,  ,,1,  uJ,  i-'7.  Mi,  i4«,  liS.  ■'«,  ■''-■•  CJeolo^y  of 
Minn.',  iMnal  Report,  Vol.  II,  p.  550.     Geol.  and  Nal.  Hist.  Survey  of  Canada,   Annual   Report, 

Vol.  IV,  lip.  4'.  4J  K. 

,.;.i    Geolouy  of  X.  H.,  Vol.  Ill,  p.  i,,. 

I  ;i.  liulletin,  <;.  S.  A.,  Vol.  I,  pp.  !.,,5 -sj:;,  with  -.ection-,.  1'roi.eedinK^  of  tlie  lioston  Society 
of  N'.itaral  H\  ■■  iry,  vol.  XXV,  i^jj,  pp.  477-4JJ. 


200 


OCHKSIKR    ACADIMV    uK    SCII' NCK. 


IJ 


m.  9. 


f  the  beds  forming  the  edReof  the  plains  where  theyadjoinec 


the  ice.sheet.  and  attribmen  it  t.,  the  v.ptlow  of  siil);;lacial  waters 
bringing  with  them  the  sediments  whie.ii  make  the  pla>n  and  reach  to 
a  considerable  distance,  having  in  their  lower  portion,  on  the 
greater  part  of  their  area,  the  forwardly  dipping  stratif.cation  that  is 
characteristic  of  deltas  or  of  deposits  swept  by  torrential  currents  into 
the  slowly  flowing  broad  expanse  of  lloo.led  rivers.  It  seems  to  me. 
however  more  probable  that  the  back-set  beds  were  formed  by  the 
downward  and  backward  transfer  of  sand  from  the  surface  of  the 
plain,  to  till  in  succession  the  small  spaces  from  which  the  ice-sheet 
was  gradually  withdrawn. 

P.ecause  the  summer  melting  of  the  North  American  loe-sheet  m 
the  Champlain  epoch,  or  closing  stage  of  the  Ciacial  period,  was  far 
more  rapid  than  that  of  the  Alaskan  glaciers  at  the  present  day.  the 
previously  existing  small  subglacial  stream-courses  were  inadeciuate 
for  the  transportation  of  the  large  supplies  of  englacial  drift  then  set 
free  by  which,  indeed,  the"  subglacial  tunnels  appear  to  have  been 
mos'tlv  obstructed  and  closed.  The  waters  of  the  glacial  melting  and 
of  accompanying  rains  therefore  Howed.  as  I  believe,  in  channels  on 
the  ice  surface,  often  near  their  mouths  more  like  canons  than  like 
ordinary  land  valleys,  there  depositing  the  eskers  and  kames. 

My  studies  of  the  Pinnacle  hills  and  I'ittsford  esker  series,  of  the 
very  massive  kame  deposits  forming  the  greater  part  of  the  outermost 
terminal  moraine  on  Long  Island  eastward  from  Roslyn  ().."f  J^l^^ 
large  kame  called  the  Devil's  Heart,  rising  in  a  somewhat  conical  hill 
,,.  feet  above  the  adj<.ining  country  south  of  Devil's  lake  in  North 
Dakota  and  of  the  esker  named  liird's  hill,  seven  miles  northeast  of 
Winnipeg  C),  seem  to  me  to  demonstrate,  beyond  all  doubt,  that 
their  material,  and  probably  likewise  that  of  eskers  and  kames  gener- 
ally was  supplied  by  superglacial  streams  from  the  plentiful  englac.al 
driVt,  and  could  not  have  been  brr.ught  from  drift  beneath  the  ice  by 
subglacial  drainage. 


(11. 
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